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As I said in title? How a wifi/bluetooth speaker can get audio data from your device such as phone or PC? I have an bluetooth speaker and any sound from my phone is sent to that speaker - How they can do that. Even with wifispeaker, I see that some must run with a program, but some doesn't. Just turn on speaker, connect to your device and you can stream any sound to it.

Thank you

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  • For Bluetooth it's A2DP, a standard protocol used by most devices, it's not Apple-specific and is compatible with a wide range of devices. For Wi-Fi (or Ethernet, as it only requires an IP connection, the physical link doesn't matter) it's Airplay, an Apple-specific technology that uses Bonjour (Zeroconf) for device discovery, and RTSP for the audio data itself. More info : theiphonewiki.com/wiki/AirPlay and git.zx2c4.com/Airtunes2/about
    – user56648
    Commented Mar 13, 2015 at 20:29

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This page on the Bluetooth specification website very quickly descends into technobabble, but the Advanced Audio Distribution Profile is how audio is distributed, or sent, from a Bluetooth audio transmitter (such as iPhone or iPod) to a Bluetooth audio receiver (such as headphones or a stand-alone speaker).

I am not sure how technical of an answer you are looking for, but the page linked above goes into much more detail.

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On re-reading, this may not be the actual answer… if it's bluetooth, then it's bluetooth - but if it works in Airplane mode, then read on...

Simply put, they work by induction.
They actually 'listen' to the magnetic field in the phone's speaker itself.

If you pass an alternating current through a wire wrapped round a magnet, the current will induce a magnetic field, causing the magnet to move.
If you attach that magnet to a paper or plastic cone - you have a speaker.

Conversely, if you vibrate that cone, you induce a current in the wire coil - & there you have a microphone.

The magnetic field generated by the speaker coil is very low, but is just strong enough that if you put a 'receiver' consisting of another coil & magnet, you can generate just enough current to power a small amplifier, which can then re-transmit that to a new speaker as amplified sound.

[There must be some kind of shielding or suppression circuit in there to prevent it 'hearing' itself, but that's above my expertise-level]

You can test this theory very simply…
Put your iPhone in Airplane mode & test it on the speaker.
The phone is not transmitting anything by radio, so it must be induction.

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  • While this is possible in theory, do you actually know any speakers that use this technology ? I really don't see the point of it, as using Bluetooth or just a plain old Lightning connector is way easier and provides better quality.
    – user56648
    Commented Mar 13, 2015 at 20:25
  • @AndréDaniel Yes - I tested it with my own [rather cheap] induction speakers. (I'm also an audio engineer, so I over-simplified the structure, but the theory is sound [pardon the pun] nonetheless) Induction is a system that will work with any device with a speaker in it - far less hi-tech than bluetooth/wifi, but fine for low-rez repro of an iPod if you're on holiday in Greece etc. I wouldn't use it to check my latest mix ;)
    – Tetsujin
    Commented Mar 13, 2015 at 20:31
  • But this requires the phone to be extremely close to the induction receiver coil, right ? In this case, again, using the Lightning connector or the audio jack seems easier and more reliable, so I doubt a commercial product would use that induction technology.
    – user56648
    Commented Mar 13, 2015 at 20:36
  • On it, yes. It's still a valid method - lot cheaper than providing interface to all the current phone connectors/protocols. [I'm not claiming it's good, merely that it exists]
    – Tetsujin
    Commented Mar 13, 2015 at 20:39

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